Alabama is suing the Trump administration to force the Census Bureau not to count undocumented people as part of the decennial tally used to determine how many seats in Congress each state gets.

The suit signals a continued conservative interest in changing the way the census counts immigrants. In a statement, Rep. Mo Brooks (R-Ala.), one of the plaintiffs in the suit, said apportionment should exclude immigrants and be based on only the citizen population. Rep. Steve King (R-Iowa) and Kansas Secretary of State Kris Kobach (R) have made similar calls. Missouri lawmakers are considering legislation to base their state legislative districts based only on citizen population.

Last week the top official in the Department of Justice’s civil rights division said the Trump administration had “no position” on whether districts should be apportioned based solely on citizen population.

Every 10 years, the census counts all people in the United States, regardless of their immigration status, and that tally is used as the basis to figure out how many congressional seats each state gets. The14th Amendment says congressional seats should be apportioned based on simply the number of “persons.”

But in a suit filed Tuesday in federal court in Alabama, Brooks and the state’s Attorney General Steve Marshall (R) argue that in the 18th and 19th centuries, the word “persons” would not have been understood to include undocumented people in the country. They argue that including undocumented immigrants in the count to determine congressional representation unfairly allows states with large undocumented populations to have inflated political representation. Alabama is projected to lose a congressional seat after the next census.

In March the Commerce Department announced it would add a question asking about citizenship to the 2020 census ― the first time it will do so on a decennial survey since 1950. Civil rights groups say including the question will drive down response rates among immigrant groups.

The results of the census have significant consequences; in addition to determining how many House seats each state gets, the count determines how hundreds of billions of dollars in federal funds are allocated.

The suit seeks to block a census rule directing the bureau to count citizens and foreign nationals in the United States at the address where they live or sleep most of the time. The plaintiffs argue that the rule violates the 14th Amendment “by robbing the people of the state of Alabama of their rightful share of political representation while systematically redistributing political powers to states with high numbers of illegal aliens and their citizens.”

Legal experts and historians cast doubt on the lawsuit’s foundational claim ― that the word “persons” was previously understood to exclude undocumented immigrants.

Franita Tolson, a law professor at the University of Southern California and a scholar of the 14th Amendment, said she was “unaware of any historical support” for Alabama’s argument. She said the legislative history surrounding the 14th Amendment shows that those who passed it understood the word “persons” to apply to those ineligible at the time to become citizens.

“To say that Alabama’s argument is a stretch is being overly generous,” she wrote in an email. “The text says ‘persons’ and the history illustrates that this term applies broadly.”

Michael Ramsey, a law professor at the University of San Diego, noted that the founders added a clause to Article I, Section 2 of the Constitution to prevent slaves from being counted as people for the purpose of determining how many congressional seats each state gets. If the Founding Fathers had intended to exclude people illegally in the United States, he said, they could have added a clause to explicitly say so.

Pamela Karlan, a professor at Stanford Law School, pointed to information on the website of United States Customs and Immigration Services noting that immigration in the 18th and 19th centuries was “relatively free and open.” It wasn’t until 1875 that the U.S. Supreme Court said the federal government had a responsibility to regulate immigration, and it wasn’t until 1880 that Congress began to enact immigration legislation.

“At the time of the Founding, there simply wasn’t a category of ‘undocumented’ immigrants,” she wrote in an email.

John Thompson, a former director of the Census Bureau, noted that there is no good way for the census to determine whether people are in the country legally. Census officials, he said, can’t simply walk up to people and ask them if they are legally in the United States and expect to get an accurate count.

The suit offers no method for the Census Bureau to count legal immigrants but exclude unauthorized residents.

Mike Lewis, a spokesman for Marshall, dismissed the practical concerns.

“It is important to know who is here both legally and illegally. Our lawsuit is only focused on the question of counting illegal immigrants in the apportionment portion of the census,” he said in a statement. “There are a variety of proposals that would allow the census to identify immigrants without legal status. We will address the appropriate remedy in the course of the litigation.”

Jeffrey Wice, a Washington lawyer who has worked with Democrats on redistricting issues, said the case could go to the Supreme Court. He added that it was “fiction” that the Founding Fathers intended to exclude undocumented people from the census.